The minimum important difference for the PREM-9 following a course of Pulmonary Rehabilitation (PR)

Introduction: The PREM-9 questionnaire is designed to help health care professionals learn more about the patients’ experience of living with COPD. A significant change has previously been reported after pulmonary rehabilitation (PR)1,2. The MID for the PREM-9 after a course of PR has not been established. Aims: To define a meaningful change in PREM-9 following PR. Methods: Patients with COPD attending a twice weekly 6 week outpatient PR programme completed the PREM-9 questionnaire pre and post PR. A number of statistical methods were used to determine the MID including the distribution based method of 0.5xSD of the change, an anchor based method using the Hospital Anxiety and Depression Scale (HADS) anxiety domain as well as receiver operating characteristic (ROC) analysis. Results: 69 patients (35 males; mean [SD] FEV1 (%) 57.3 [19.6] %, age 66 [10.2] years) completed the PREM-9 questionnaire. A significant mean change was noted for the PREM-9 of -3.14 (SD 7.33, p<0.01). The distribution method (0.5 x SD) yielded an MID of -3.67. There was a weak positive correlation between the PREM-9 questionnaire change when anchored with the change in HADS anxiety domain (r=0.35, p<0.05). The change in PREM-9 for responders (defined as HADS anxiety MID ≥ -1.5) was -5.26 (SD 8.33). Sensitivity and specificity analysis using ROC using HADS anxiety anchor yielded a change of -7.5 units. Conclusions: The calculated MID is between -3.67 and -7.5 units. Further research is required to confirm an anchor based MID. 1Chavaillaz S et al. Thorax 2021;76:A104. 2Hodson M et al. Thorax 2019;74:600–603.